Across the Bay Area — from Pittsburg to San Francisco, from Tiburon to Gilroy — you’re being watched.

And it’s not just the National Security Agency secretly vacuuming up your personal data. Local police agencies are increasingly adopting Big Data technologies such as automatic license-plate readers that gather information about everyone, whether they’ve broken the law or not.

A lot of the information ends up on the 14th floor of a federal office building in San Francisco, where a “fusion center” run by state and local law enforcement agencies combines the data with a plethora of personal information about you, from credit reports to car rentals to unlisted phone numbers to gun licenses.

“No one has any idea of the scale of information being gathered,” said Mike Katz-Lacabe, of San Leandro, who discovered this in a very personal way.

A San Leandro school board member, Katz-Lacabe said a comment he heard about license-plate readers at a city council meeting prompted him to file public-records requests that revealed not only that his Toyota Tercel’s license plate had been photographed all over town, but also that it and all kinds of other information were being collated at the fusion center. “I was a little shocked,” he said.

Along with many of the nation’s 77 other fusion centers, the Northern California Regional Intelligence Center was created after the Sept. 11, 2001, attacks as an antiterrorism intelligence hub. And like many of the other centers, it has morphed into a huge data center whose purpose is to solve and prevent all kinds of crimes — from terrorist bombings to car thefts.

Authorities insist there’s nothing for law-abiding people to worry about. They say they’re just using the latest technology to gather and consolidate information they’ve used for years — extra eyes and ears in an age of skimpy budgets and understaffed beats.

Police are also beefing up their use of video surveillance. The latest Bay Area trend allows patrol officers to view surveillance video 24/7 on their smartphones. Many Bay Area police agencies now have at least some cruisers fitted with automatic license-plate readers to scan every car they pass. This and reams of other data from 15 other counties are fed to the fusion center, where analysts search for patterns indicating suspicious activity.

Mike Sena, the Northern California fusion center’s director, said his agency is simply centralizing law-enforcement information that was fragmented in the past.

“Before it would be hit or miss,” he said in his office at the center, which overlooks San Francisco’s Civic Center. He’s quick to reject any analogies between his agency and the NSA: “We’re not some big spy shop.”

California’s six fusion centers have been credited with tracking down men who made bomb threats to Delta Air Lines and the U.S. Embassy in Italy; foiling an attempted kidnapping in Sacramento; and helping to quickly find a suspicious tractor-trailer reportedly headed for New York’s Times Square — though the truck, when found, was deemed harmless.

But some Bay Area police collect data for more prosaic purposes.

Tiburon in 2010 installed cameras on the only two roads in and out of town so police now record the license plate of every car that enters and leaves, creating what some say is a virtual gated community.

Police Chief Michael Cronin said he had to convince the Town Council and residents that it wasn’t unduly intrusive because it captures only plates and not images of the cars’ occupants. Property crimes, he said, have decreased by about a third since the well-publicized cameras were installed.

The Piedmont City Council likes the idea: It voted June 3 to spend $679,000 to install 39 license-plate readers at 15 points around the city. And Menlo Park’s police chief says he wants to do the same.

Nicole Ozer, technology and civil liberties policy director at the American Civil Liberties Union of Northern California, said the more data that’s accrued and the longer it’s kept, the more potential for abuse exists. “It has very limited efficacy and real potential for harm,” she said.

Other “eyes” are watching you, too.

Video cameras have become commonplace in many homes and almost every business, ATM or public building. Yet many people might not realize that police across the Bay Area use their own video surveillance systems to keep tabs on public areas, too.

A consultant’s recent report to the Oakland Police Department urged it to “significantly increase the camera-monitoring capabilities of the OPD in commercial areas throughout the city to provide identifications and evidence in robbery, burglary and some shooting cases. Cameras would be monitored and recorded at the Domain Awareness Center that is currently under construction.”

Pittsburg police officers can now watch live video from 89 cameras throughout the city on their smartphones while out on their beats. Lt. Ron Raman said the cameras essentially let officers extend their enforcement and investigative reach.

Gilroy police Capt. Jim Gillio said the city’s Downtown Merchants Association paid half of the $50,000 cost for a six-camera system, of which three cameras have been installed, so emergency dispatchers can tilt, pan and zoom in if something’s happening. Gillio said the system has helped spot stolen cars and once let dispatchers quickly see that a reported kidnapping actually hadn’t happened.

Richmond police Capt. Mark Gagan said “no police manager would say one technology or one method is a panacea for all crimes,” but his department’s 42 cameras — placed in violent areas as well as areas often fouled by quality-of-life issues such as garbage dumping, vandalism and prostitution — help a thinly spread police force stay atop of what’s going on and have led to many arrests. Retired police officers, who both “understand what suspicious or predatory behavior looks like” and know the city’s geography well, monitor the live feeds 12 to 16 hours a day, he said.

Felix Hunziker, a 47-year-old architect and Richmond resident who’s involved with the North & East Neighborhood Council’s residents’ patrol, said he’s “pretty much good with it because we do have problems in our city, and the cameras are useful tools. … They have been useful in solving crimes; they may be a deterrent, as well.”

Palo Alto, Redwood City, San Pablo, Pinole, Martinez and other Bay Area cities have cameras, too, but most don’t mention it on their websites. You wouldn’t know about the cameras unless you specifically asked police or city officials.

San Francisco’s policy prohibits police from monitoring their cameras in real time; officers review recordings only after a crime has occurred. But after the Boston Marathon bombing in April, the chief asked that the policy be modified during big events. He also asked for more cameras.

UC Berkeley researchers’ 2008 analysis of San Francisco’s cameras found they had no deterrent effect on violent crime, though certain property crimes — such as pickpocketing, purse-snatching and thefts from cars — did decrease in areas where the cameras are located.

Camera systems already in place can have software added later that will recognize people’s faces or specific objects, making all that recorded footage much more searchable and potentially invasive. It’s a booming business: Intelligent video surveillance and analytics software is a $13.5 billion industry projected to almost triple to $39 billion by 2020, according to a March report from Homeland Security Research, a market research firm.

Legal doctrines supporting the government’s collection of information in public spaces date to the 1960s, long before police could easily record so many aspects of our lives, said Shayana Kadidal, an attorney at the Center for Constitutional Rights in New York.

“The technology simply didn’t exist to allow for the government to have a camera on every street corner and record that information forever,” Kadidal said. “It doesn’t matter whether they actually use it to prosecute people. … Just knowing that the information is out there casts a huge chilling effect across society.”

Don’t want to be watched? It’s easy: Just don’t do anything, go anywhere or talk to anybody. But if you still want to live your life, there are several things you can do to reduce your exposure to government and law-enforcement snooping:Ditch the smartphone. Even with the “location services” function switched off, your phone still might use local cell towers and Wi-Fi hot spots to determine its location so long as there’s a battery in it. And, of course, your carrier is logging who you call and for how long — data we now know the government collects. If you can’t stand being out of touch, buy a “burner” prepaid phone with no contract and use a prepaid calling card to pay for calls.Get rid of your credit and debit cards. Using a credit or debit card that’s in your name is like turning on a big neon “I’M OVER HERE, AND THIS IS WHAT I’M BUYING” light above your head. Instead, use cash to buy gift cards from companies like Visa or American Express.Ride a bike or take public transit. Driving without a license plate can lead to a ticket for driving without registration; driving with someone else’s license plate can get you arrested. So if you want to avoid all those automatic license-plate readers out there, start pedaling or hop a bus or train.Encrypt your online communications and hide your IP address. From email to video chats, you can choose services and applications that will make it very hard — though perhaps not impossible — for anyone but the intended recipient to see, or to trace where your computer activity originates.Protect your data. Online or on your own computer, use long, random passwords; use different passwords for every website; change your passwords often; and store those passwords in an encrypted “password safe” app. Also consider using file or disk encryption software. And to avoid malware spies, use the latest version of your operating system and firewall software while keeping your most sensitive information on devices not connected to the Internet at all.